Knee prosthesis



FIG. 1 is a perspective view of a knee prosthesis showing my new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a back elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines where shown are for illustrative purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a knee prosthesis, as shown and described. 